A forced-air system heats air in a furnace and uses a fan to force the warmed air through ductwork to the home's rooms.
As the warmed air is pumped into the room, it is mixed with the cooler existing air until the desired room temperature is achieved. At the same time as warmed air is being pumped into a room, some of the older, cooler air in the room is pushed into the return air ductwork to be reheated and recycled through the home.
A boiler system heats fluid (typically water, glycol or a mixture) and pumps the warmed fluid to a heat exchanger such as an in-floor system or baseboard radiator.
The baseboard radiator or floor conducts heat from the heated fluid. This heat is transferred via radiation to the rooms' objects. As cooler air comes in contact with warm objects (including the radiator), it warms and rises, creating a convective loop, mixing to the desired temperature.
Heat naturally flows from warm to cool zones. A heat pump is a machine that reverses this, taking heat from a cooler area and pumping it to warmer zone. Heat pumps require electricity to operate, about 34 percent of the nation’s electricity is produced from coal.
Learn more about gas & electric system efficiency (PDF).
Ground Source (Geothermal) Heat Pumps
A ground source heat pump can heat or cool a home by either:
- Collecting heat from the ground and pumping it inside to provide home heating, or
- Cooling the home by collecting heat from the home and pumping it into the ground.
geothermal is sometimes used to describe a ground source heat pump system. However, a geothermal heat pump is actually a system that taps into really hot areas (hundreds of degrees) beneath the earth for district heating or electric generation. Areas of the world with geysers and active volcanoes, such as Iceland, utilize geothermal energy.
A ground source heat pump typically requires a supplemental heating system for below zero temperatures and later in the heating season when the latent heat in the ground has been exhausted. Get the facts on
geothermal heat pumps vs. a high-efficiency natural gas furnace (PDF).
In addition, the payback on a ground source heat pump can exceed 25 years.
Air Source Heat Pumps (hybrid)
An air-source heat pump collects heat from the outside air during the fall and spring heating seasons and delivers it to the home exactly the same as a home's air conditioner would if operated in reverse.
When temperatures are about 35 degrees or colder, an air source heat pump cannot deliver enough heat to the home and another heating system will be needed. In the summer, an air source heat pump operates just as an air conditioner does, taking heat from the home and pumping it outside. Learn more about
air source heat pumps vs. a high-efficiency natural gas furnace (PDF).
Electric Resistance Heating
Electric resistance heating converts nearly 100 percent of the energy in the electricity to heat. However, electricity is produced from power generators that deliver only about 27 percent of the fuel's energy and have a very heavy impact on the environment.
Electric resistance heating is significantly more expensive than heating your home with natural gas. Use our
operating cost calculator to see how you could benefit from choosing natural gas versus electricity.